FAA-H-8083-23, Seaplane, Skiplane, and Float/Ski Equipped

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PREFLIGHT INSPECTIONBegin the preflight inspection with a thorough reviewof the existing local weather, destination weather, andwater conditions. This weather evaluation shouldinclude the direction and speed of the wind to deter-mine their effects on takeoffs, landings, and otherwater operations.

The preflight inspection of a seaplane is somewhat dif-ferent from that of a landplane. Inspecting a seaplaneon the water is complicated by the need to repositionthe seaplane to gain access to all parts of the airframe.On the other hand, preflighting a seaplane on land maycreate certain challenges because the wings and tailsurfaces may be out of reach and difficult to inspectwhen standing on the ground.

The following preflight description omits many itemsthat are identical in landplanes and seaplanes in orderto emphasize the differences between the two proce-dures. The process and the equipment to be checkedvary from airplane to airplane, but the followingdescription provides a general idea of the preflightinspection for a typical high wing, single-engine float-plane. As always, follow the procedures recommendedin the Airplane Flight Manual (AFM) or Pilot’sOperating Handbook (POH).

If the seaplane is in the water during the preflight, takea good look at how it sits on the surface. This can pro-vide vital clues to the presence of water in the floats, aswell as to the position of the center of gravity. Is theseaplane lower in the water than it should be, given itsload? Is one wing lower than the other, or is one floatriding noticeably lower in the water than the other? Arethe sterns of the floats low in the water? If any of thesesigns are present, suspect a flooded float compartmentor an improperly loaded seaplane. At more than 8pounds per gallon, even a relatively small amount ofwater in a float compartment can seriously affect bothuseful load and center of gravity (CG).

In the cockpit, verify that the throttle is closed, themixture control is full lean, and the magnetos andmaster switch are turned off. Lower the water ruddersand check for any stiffness or binding in the action ofthe cables. Check that necessary marine and safetyequipment, such as life vests, lines (ropes), anchors,and paddles are present, in good condition, andstowed correctly. Obtain the bilge pump and fuelsample cup.

Standing on the front of the float, inspect the propeller,forward fuselage, and wing. Check the usual items,working from the nose toward the tail. Water spray dam-age to the propeller looks similar to gravel damage, andmust be corrected by a mechanic. Check the oil and fuellevels and sample the fuel, ensuring that it is the propergrade and free of contaminants. Naturally, the mostlikely contaminant in seaplane fuel tanks is water. Payextra attention to the lubrication of all hinges. Not onlydoes lubrication make movement easier, but a good coat-ing of the proper lubricant keeps water out and preventscorrosion. Look for any blistering or bubbling of thepaint, which may indicate corrosion of the metal under-neath. Check the security of the float struts and theirattachment fittings. Be careful moving along the float,and pay attention to wing struts, mooring lines, and otherobstacles. If the seaplane is on land, do not stand on thefloats aft of the step or the seaplane may tip back.

Next, inspect the float itself. Water forces can createvery high loads and lead to cumulative damage. Lookcarefully for signs of stress, such as distortion or buck-ling of the skin, dents, or loose rivets. The chinesshould form a continuous smooth curve from front toback, and there should be no bends or kinks along theflange. If the floats are made of fiberglass or compositematerials, look carefully for surface cracks, abrasions,or signs of delamination. Check the spreader barsbetween the floats, and look at the bracing wires andtheir fittings. Any sign of movement, loose fasteners,broken welds, or a bracing wire that is noticeablytighter or looser than the others is cause for concern.Check for signs of corrosion, especially if the seaplanehas been operated in salt water. Although corrosion is

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less of an issue with composite floats, be sure to checkmetal fittings and fasteners. [Figure 4-1]

Use the bilge pump to remove any accumulated waterfrom each watertight compartment. The high dynamicwater pressure and the physical stresses of takeoffs andlandings can momentarily open tiny gaps between floatcomponents, allowing small amounts of water to enter.Conversely, sitting idle in the water also results in asmall amount of seepage and condensation. While it isnormal to pump a modest amount of water from eachcompartment, more than a quart or so may indicate aproblem that should be checked by a qualified aircraftmechanic experienced in working on floats. Normal isa relative term, and experience will indicate how muchwater is too much. [Figure 4-2]

If pumping does not remove any water from a compart-ment, the tube running from the bilge pump opening tothe bottom of the compartment may be damaged or

loose. If this is the case, there could be a significantamount of water in the compartment, but the pump isunable to pull it up. [Figure 4-3] Be sure to replace theplugs firmly in each bilge pump opening.

At the stern of the float, check the aft bulkhead, or tran-som. This area is susceptible to damage from the waterrudder moving beyond its normal range of travel.Carefully check the skin for any pinholes or signs ofdamage from contact with the water rudder or hingehardware. Inspect the water rudder retraction and steer-ing mechanism and look over the water rudder for anydamage. Remove any water weeds or other debrislodged in the water rudder assembly. Check the waterrudder cables that run from the float to the fuselage.[Figure 4-4]

Figure 4-1. A preflight inspection with the seaplane on landprovides an opportunity to thoroughly examine the floatsbelow the waterline. Note the spray rail on the inboard chineof the far float in this photo.

Figure 4-2. Bilge pump openings are closed with a soft rub-ber ball.

Figure 4-3. Be suspicious if pumping does not remove asmall amount of water. If the bilge pump tube is damaged,there may be water in the compartment that the pump can-not remove.

Figure 4-4. Inspect the water rudders, cables, springs, andpulleys for proper operation.

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engine. With oil pressure checked, idle r.p.m. set, andthe seaplane taxiing in the desired direction, the pilotthen fastens the seatbelt and shoulder harness, securesthe door, and continues preparing for takeoff.

When a qualified person is available to help launch theseaplane, the pilot can strap in, close the door, and startthe engine while the helper holds the seaplane. In mostsituations, the helper should position the seaplane so itis facing outward, perpendicular to the dock. It is veryimportant that the helper have experience in the properhandling of seaplanes, otherwise an innocent mistakecould cause serious damage to the seaplane or tonearby boats, structures, or other seaplanes.

TAXIING AND SAILINGOne major difference between taxiing a landplane andtaxiing a seaplane is that the seaplane is virtuallyalways in motion, and there are no brakes. Whenidling, a landplane usually remains motionless, andwhen moving, brakes can be used to control its speedor bring it to a stop. But once untied, the seaplanefloats freely along the water surface and constantlymoves due to the forces of wind, water currents,propeller thrust, and inertia. It is important that theseaplane pilot be familiar with the existing wind andwater conditions, plan an effective course of action,and mentally stay ahead of the seaplane.

There are three basic positions or attitudes used inmoving a seaplane on the water, differentiated by theposition of the floats and the speed of the seaplanethrough the water. They are the idling or displacementposition, the plowing position, and the planing or stepposition.

IDLING POSITIONIn the idling position or displacement position, thebuoyancy of the floats supports the entire weight ofthe seaplane and it remains in an attitude similar tobeing at rest on the water. Engine r.p.m. is kept as lowas possible to control speed, to keep the engine fromoverheating, and to minimize spray. In almost all cir-cumstances, the elevator control should be held all theway back to keep the nose as high as possible and min-imize spray damage to the propeller. This alsoimproves maneuverability by keeping more of thewater rudder underwater. The exception is when astrong tailwind component or heavy swells couldallow the wind to lift the tail and possibly flip theseaplane over. In such conditions, hold the elevatorcontrol forward enough to keep the tail down.[Figure 4-5 on next page]

To check the empennage area, untie the seaplane, gen-tly push it away from the dock, and turn it 90° so thetail extends over the dock. Take care not to let the waterrudders contact the dock. In addition to the normalempennage inspection, check the cables that connectthe water rudders to the air rudder. With the air ruddercentered, look at the back of the floats to see that thewater rudders are also centered. (On some systems,retracting the water rudders disengages them from theair rudder.) If the seaplane has a ventral fin to improvedirectional stability, this is the time to check it. Sprayfrequently douses the rear portion of the seaplane, sobe particularly alert for signs of corrosion in this area.

With the empennage inspection complete, continueturning the seaplane to bring the other float against thedock, and tie it to the dock. Inspect the fuselage, wing,and float on this side. If the seaplane has a door on onlyone side, turn the seaplane so the door is adjacent to thedock when the inspection is complete.

When air temperatures drop toward freezing, icebecomes a matter for concern. Inspect the float com-partments and water rudders for ice, and consider thepossibility of airframe icing during takeoff due tofreezing spray. Water expands as it freezes, and thisexpansion can cause serious damage to floats. A largeamount of water expanding inside a float could causeseams to burst, but even a tiny amount of water freez-ing and expanding inside a seam can cause severeleakage problems. Many operators who remove theirfloats for the winter store them upside down with thecompartment covers off to allow thorough drainage.When the time comes to reinstall the floats, it’s a goodidea to look for any bugs or small animals that mighthave made a home in the floats.

STARTING THE ENGINECompared to a landplane, a seaplane’s starting proce-dures are somewhat different. Before starting theengine, the seaplane usually needs to be pushed awayfrom the dock, and quite often, it is the pilot whopushes off. Therefore, the pilot should perform asmany of the items on the starting checklist as possibleprior to shoving off. This includes briefing passengersand seeing that they have fastened their seatbelts. Thepassenger briefing should include procedures for evac-uation, the use of flotation gear, and the location andoperation of regular and emergency exits. All passen-gers are required to be familiar with the operation ofseatbelts and shoulder harnesses (if installed). Whenthe engine is primed and ready to start, the pilot leavesthe cockpit, shoves off, returns to the pilot’s seat,quickly turns on the master switch and magnetos, veri-fies that the propeller area is clear, and starts the

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Use the idling or displacement position for most taxi-ing operations, and keep speeds below 6-7 knots tominimize spray getting to the propeller. It is especiallyimportant to taxi at low speed in congested or confinedareas because inertia forces at higher speeds allow theseaplane to coast farther and serious damage can resultfrom even minor collisions. Cross boat wakes or swellsat a 45° angle, if possible, to minimize pitching orrolling and the possibility of an upset.

PLOWING POSITIONApplying power causes the center of buoyancy to shiftback, due to increased hydrodynamic pressure on thebottoms of the floats. This places more of the sea-plane’s weight behind the step, and because the floatsare narrower toward the rear, the sterns sink fartherinto the water. Holding the elevator full up also helpspush the tail down due to the increased airflow fromthe propeller. The plowing position creates high drag,requiring a relatively large amount of power for amodest gain in speed. Because of the higher r.p.m.,the propeller may pick up spray even though the noseis high. The higher engine power combined with lowcooling airflow creates a danger of heat buildup in theengine. Monitor engine temperature carefully to avoidoverheating. Taxiing in the plowing position is not

recommended. It is usually just the transitional phasebetween idle taxi and planing. [Figure 4-6]

PLANING OR STEP POSITIONIn the planing position, most of the seaplane’s weightis supported by hydrodynamic lift rather than thebuoyancy of the floats. (Because of the wing’s speedthrough the air, aerodynamic lift may also be support-ing some of the weight of the seaplane.)Hydrodynamic lift depends on movement through thewater, like a water ski. As the float moves fasterthrough the water, it becomes possible to change thepitch attitude to raise the rear portions of the floatsclear of the water. This greatly reduces water drag,allowing the seaplane to accelerate to lift-off speed.This position is most often called on the step. [Figure4-7]

There is one pitch attitude that produces the minimumamount of drag when the seaplane is on the step. Anexperienced seaplane pilot can easily find this “sweetspot” or “slick spot” by the feel of the floats on thewater, but the beginning seaplane pilot usually needsto rely on gauging the position of the nose on the hori-zon. If the nose is considerably high, the rear portionsof the floats contact the water, drag increases, and the

Figure 4-5. Idling position.The engine is at idle r.p.m., the seaplane moves slowly, the attitude is nearly level, and buoyancy sup-

ports the seaplane.

Figure 4-6. Plowing position.

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seaplane tends to start settling back into more of aplowing position. If the nose is held only slightlyhigher than the ideal planing attitude, the seaplanemay remain on the step but take much longer to accel-erate to rotation speed. On the other hand, if the noseis too low, more of the front portion of the float con-tacts the water, creating more drag. This condition iscalled dragging, and as the nose pulls down and theseaplane begins to slow, it can sometimes feel similarto applying the brakes in a landplane.

To continue to taxi on the step instead of taking off,reduce the power as the seaplane is eased over onto thestep. More power is required to taxi with a heavy load.However, 65 to 70 percent of maximum power is agood starting point.

Taxiing on the step is a useful technique for coveringlong distances on the water. Carefully reducing poweras the seaplane comes onto the step stops accelerationso that the seaplane maintains a high speed across thewater, but remains well below flying speed. At thesespeeds, the water rudders must be retracted to preventdamage, but there is plenty of airflow for the air rudder.With the seaplane on the step, gentle turns can be madeby using the air rudder and the ailerons, always main-taining a precise planing attitude with elevator. Theailerons are positioned into the turn, except whenaileron into the wind is needed to keep the upwind wingfrom lifting.

Step taxiing should only be attempted in areas where thepilot is confident there is sufficient water depth, no float-ing debris, no hidden obstructions, and no other watertraffic nearby. It can be difficult to spot floating hazardsat high speeds, and an encounter with a floating log orother obstruction could tear open a float. Your seaplaneis not as maneuverable as craft that were designed forthe water, so avoiding other vessels is much more diffi-cult. Besides the obvious danger of collision, otherwater traffic creates dangerous wakes, which are a

much more frequent cause of damage. If you see thatyou are going to cross a wake, reduce power to idleand idle taxi across it, preferably at an angle. Nevertry to step taxi in shallow water. If the floats touchbottom at high speed, the sudden drag is likely to flipthe seaplane.

From either the plowing or the step position, whenpower is reduced to idle, the seaplane decelerates quiterapidly and eventually assumes the displacement oridle position. Be careful to use proper flight controlpressures during the deceleration phase because asweight is transferred toward the front of the floats anddrag increases, some seaplanes have a tendency to noseover. Control this with proper use of the elevator.

TURNSAt low speeds and in light winds, make turns using thewater rudders, which move in conjunction with the airrudder. As with a landplane, the ailerons should bepositioned to minimize the possibility of the wind lift-ing a wing. In most airplanes, left turns are somewhateasier and can be made tighter than right turns becauseof torque. If water rudders have the proper amount ofmovement, most seaplanes can be turned within aradius less than the span of the wing in calm conditionsor a light breeze. Water rudders are usually more effec-tive at slow speeds because they are acting in compar-atively undisturbed water. At higher speeds, the sternof the float churns the adjacent water, causing the waterrudder to become less effective. The dynamic pressureof the water at high speeds may tend to force the waterrudders to swing up or retract, and the pounding cancause damage. For these reasons, water rudders shouldbe retracted whenever the seaplane is moving at highspeed.

The weathervaning tendency is more evident in seaplanes,and the taxiing seaplane pilot must be constantly aware ofthe wind’s effect on the ability to maneuver. In strongerwinds, weathervaning forces may make it difficult to turn

Figure 4-7. On the step. The attitude is nearly level, and the weight of the seaplane is supported mostly by hydrodynamic lift.Behind the step, the floats are essentially clear of the water.

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downwind. Often a short burst of power provides suf-ficient air over the rudder to overcome weathervan-ing. Since the elevator is held all the way up, theairflow also forces the tail down, making the waterrudders more effective. Short bursts of power arepreferable to a longer, continuous power application.With continuous power, the seaplane accelerates,increasing the turn radius. The churning of the waterin the wake of the floats also makes the water ruddersless effective. At the same time, low cooling airflowmay cause the engine to heat up.

During a high speed taxiing turn, centrifugal forcetends to tip the seaplane toward the outside of the turn.When turning from an upwind heading to a downwindheading, the wind force acts in opposition to centrifu-gal force, helping stabilize the seaplane. On the otherhand, when turning from downwind to upwind, thewind force against the fuselage and the underside ofthe wing increases the tendency for the seaplane to leanto the outside of the turn, forcing the downwind floatdeeper into the water. In a tight turn or in strong winds,the combination of these two forces may be sufficientto tip the seaplane to the extent that the downwind floatsubmerges or the outside wing drags in the water, andmay even flip the seaplane onto its back. The further

the seaplane tips, the greater the effect of the cross-wind, as the wing presents more vertical area to thewind force. [Figure 4-8]

When making a turn into the wind from a crosswindcondition, often all that is necessary to complete theturn is to neutralize the air rudder and allow the sea-plane to weathervane into the wind. If taxiing directlydownwind, use the air rudder momentarily to get theturn started, then let the wind complete the turn.Sometimes opposite rudder may be needed to controlthe rate of turn.

Stronger winds may make turns from upwind to down-wind more difficult. The plow turn is one technique forturning downwind when other methods are inadequate,but this maneuver is only effective in certain seaplanes.It takes advantage of the same factor that reduces afloatplane’s yaw stability in flight: the large vertical areaof the floats forward of the center of gravity. In theplowing attitude, the front portion of each float comesout of the water, presenting a large vertical surface forthe wind to act upon. This tends to neutralize the weath-ervaning force, allowing the turn to proceed. At thesame time, the center of buoyancy shifts back. Sincethis is the axis around which the seaplane pivots while

Wind Force

CentrifugalForce

Wind Force

CentrifugalForce

CentrifugalForce

WindForce

CentrifugalForce

WindForce

Figure 4-8. Wind effects in turns. When the wind and centrifugal force act in the same direction, the downwind float can beforced underwater. When the wind is countered by centrifugal force, the seaplane is more stable.

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on the water, more of the fuselage is now forward ofthe axis and less is behind, further decreasing theweathervaning tendency. In some seaplanes, thischange is so pronounced in the plowing attitude thatthey experience reverse weathervaning, and tend toturn downwind rather than into the wind. Experiencedseaplane pilots can sometimes use the throttle as aturning device in high wind conditions by increasingpower to cause a nose-up position when turning down-wind, and decreasing power to allow the seaplane toweathervane into the wind. [Figure 4-9]

To execute a plow turn, begin with a turn to the right,then use the weathervaning force combined with fullleft rudder to turn back to the left. As the seaplanepasses its original upwind heading, add enough powerto place it into the plow position, continuing the turnwith the rudder. As the seaplane comes to the down-wind heading, reduce power and return to an idle taxi.From above, the path of the turn looks like a questionmark. [Figure 4-10]

Plow turns are useful only in very limited situationsbecause they expose the pilot to a number of potentialdangers. They should not be attempted in rough wateror gusty conditions. Floatplanes are least stable whenin the plowing attitude, and are very susceptible tocapsizing. In spite of the nose-high attitude, the highpower setting often results in spray damage to thepropeller. In most windy situations, it is much saferto sail the seaplane backward (as explained in thenext section) rather than attempt a plow turn.

When the seaplane is on the step, turns involve carefulbalancing of several competing forces. As the rate of

turn increases, the floats are being forced to movesomewhat sideways through the water, and they resistthis sideways motion with drag, much like an airplanefuselage in a skidding turn. More power is required toovercome this drag and maintain planing speed. Thisskidding force also tends to roll the seaplane towardthe outside of the turn, driving the outside float deeperinto the water and adding more drag on that side. Toprevent this, use aileron into the turn to keep the out-side wing from dropping. Once full aileron into thestep turn is applied, any further roll to the outside canonly be stopped by reducing the rate of turn, so paycareful attention to the angle of the wings and the feelof the water drag on the floats to catch any indicationthat the outside float is starting to submerge. Whenstopping a step turn, always return to a straight pathbefore reducing power.

At step taxi speeds, the centrifugal force in a turn is fargreater than at idle taxi speed, so the forces involved inturning from downwind to upwind are proportionatelymore dangerous, especially in strong winds. Chancesare, by the time a pilot discovers that the outside floatis going under, the accident is almost inevitable.However, immediate full rudder out of the turn andpower reduction may save the situation by reversing

Engine IdlingWater Rudder DownElevator Full Up

Add Power to AssumePlowing Attitude.Full Right AileronElevator Full Up

Full Right RudderFull Left AileronElevator Full Up

Full Left RudderFull Left AileronElevator Full Up

Reduce Power to IdleRudder as Neededto Maintain Heading

Full Left Rudder, Full Right Aileron,Elevator Full Up

Figure 4-9. In the plowing position, the exposed area at thefront of the floats, combined with the rearward shift of thecenter of buoyancy, can help to counteract the weathervan-ing tendency.

Figure 4-10. Plow turn from upwind to downwind.

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the centrifugal force and allowing the buried float tocome up.

SAILINGLandplane pilots are accustomed to taxiing by pointingthe nose of the airplane in the desired direction androlling forward. In seaplane operations, there are oftenoccasions when it is easier and safer to move the seaplanebackward or to one side because wind, water conditions,or limited space make it impractical to attempt a turn. Ifthere is a significant wind, a seaplane can be guided intoa space that might seem extremely cramped to an inexpe-rienced pilot. Sailing is a method of guiding the seaplaneon the water using the wind as the main motive force. It isa useful technique for maneuvering in situations whereconventional taxiing is undesirable or impossible. Sincethe seaplane automatically aligns itself so the nose pointsinto the wind, sailing in a seaplane usually means movingbackward.

In light wind conditions with the engine idling or off, aseaplane naturally weathervanes into the wind. If thepilot uses the air rudder to swing the tail a few degrees,the seaplane sails backward in the direction the tail ispointed. This is due to the keel effect of the floats,which tends to push the seaplane in the direction thesterns of the floats are pointing. In this situation, lift thewater rudders, since their action is counter to what isdesired. When sailing like this, the sterns of the floatshave become the front, as far as the water is concerned,but the rear portions of the floats are smaller and there-fore not as buoyant. If the wind is strong and speedstarts to build up, the sterns of the floats could start to

submerge and dig into the water. Combined with thelifting force of the wind over the wings, the seaplanecould conceivably flip over backward, so use full for-ward elevator to keep the sterns of the floats up andthe seaplane’s nose down. Adding power can alsohelp keep the floats from submerging.

If enough engine power is used to exactly cancel thebackward motion caused by the wind, the seaplane isnot moving relative to the water, so keel effect disap-pears. However, turning the fuselage a few degrees leftor right provides a surface for the wind to push against,so the wind will drive the seaplane sideways in thedirection the nose is pointed. Combining these tech-niques, a skilled pilot can sail a seaplane around obstaclesand into confined docking spaces. [Figure 4-11]

Figure 4-12 shows how to position the controls for thedesired direction of motion in light or strong winds.With the engine off, lowering the wing flaps and open-ing the cabin doors increases the air resistance andthus adds to the effect of the wind. This increases sail-ing speed but may reduce the effect of the air rudder. Ifsailing with the engine off results in too much motiondownwind, but an idling engine produces too muchthrust, adding carburetor heat or turning off one mag-neto can reduce the engine power slightly. Avoid usingcarburetor heat or running on one magneto forextended periods. Instead, start the engine briefly toslow down.

Where currents are a factor, such as in strong tidalflows or a fast flowing river, sailing techniques must

With Left Rudder and LeftAileron Down, SeaplaneMoves Downwind to the Right

With Rudder and AileronsNeutral, Seaplane MovesStraight Downwind

Engine Thrust toBalance Wind Motion

With Right Rudderand Right AileronDown, SeaplaneMoves Downwindto the Left

WaterRudders Up

Figure 4-11. When the seaplane moves through the water, keel effect drives it in the direction the tail is pointed. With no motionthrough the water, the wind pressure on the fuselage pushes the seaplane toward the side the nose is pointed.

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incorporate the movement of the water along with thewind. The current may be a help or a hindrance, orchange from a help to a hindrance when the pilotattempts to change direction. The keel effect onlyworks when the floats are moving through the water. Ifthe current is moving the seaplane, there may be littleor no motion relative to the water, even though theseaplane is moving relative to the shore. Using wind,current, and thrust to track the desired course requirescareful planning and a thorough understanding of thevarious forces at work.

With the engine shut down, most flying boats sailbackward and toward whichever side the nose ispointed, regardless of wind velocity, because the hulldoes not provide as much keel effect as floats in pro-portion to the side area of the seaplane above thewaterline. To sail directly backward in a flying boat,release the controls and let the wind steer. Sailing isan essential part of seaplane operation. Since eachtype of seaplane has its own peculiarities, practice

sailing until thoroughly familiar with that particulartype. Practice in large bodies of water such as lakesor bays, but sufficiently close to a prominent object inorder to evaluate performance.

Before taxiing into a confined area, carefully evaluatethe effects of the wind and current, otherwise the sea-plane may be driven into obstructions. With a seaplaneof average size and power at idle, a water current of 5knots can offset a wind velocity of 25 knots in theopposite direction. This means that a 5 knot currentwill carry the seaplane against a 25 knot wind.Differential power can be used to aid steering in multi-engine seaplanes.

PORPOISINGPorpoising is a rhythmic pitching motion caused bydynamic instability in forces along the float bottomswhile on the step. An incorrect planing attitude sets offa cyclic oscillation that steadily increases in amplitudeunless the proper pitch attitude is reestablished. [Figure4-13]

A seaplane travels smoothly across the water on thestep only if the floats or hull remain within a moder-ately tolerant range of pitch angles. If the nose is heldtoo low during planing, water pressure in the form of asmall crest or wall builds up under the bows of thefloats. Eventually, the crest becomes large enough thatthe fronts of the floats ride up over the crest, pitchingthe bows upward. As the step passes over the crest, thefloats tip forward abruptly, digging the bows a littledeeper into the water. This builds a new crest in frontof the floats, resulting in another oscillation. Eachoscillation becomes increasingly severe, and if not cor-rected, will cause the seaplane to nose into the water,resulting in extensive damage or possible capsizing. Asecond type of porpoising can occur if the nose is heldtoo high while on the step. Porpoising can also cause apremature lift-off with an extremely high angle ofattack, which can result in a stall and a subsequentnose-down drop into the water. Porpoising occurs dur-ing the takeoff run if the planing angle is not properlycontrolled with elevator pressure just after passingthrough the “hump” speed. The pitching created whenthe seaplane encounters a swell system while on thestep can also initiate porpoising. Usually, porpoisingdoes not start until the seaplane has passed a degree ortwo beyond the acceptable planing angle range, and

RightAileron Up

Left Rudder

Left AileronDown

Direction of Motionwith Engine Idling

Direction of Motionwith Power JustBalancing Wind

Direction of Motionwith Enough Powerto Overcome Wind

Direction of Motionwith Power Off

Figure 4-12. By balancing wind force and engine thrust, it ispossible to sail sideways or diagonally forward. Of course,reversing the control positions from those illustrated per-mits the pilot to sail to the opposite side.

Figure 4-13. Porpoising increases in amplitude if not corrected promptly.

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does not cease until after the seaplane has passed out ofthe critical range by a degree or two.

If porpoising occurs due to a nose-low planing attitude,stop it by applying timely back pressure on the elevatorcontrol to prevent the bows of the floats from digginginto the water. The back pressure must be applied andmaintained until porpoising stops. If porpoising does notstop by the time the second oscillation occurs, reduce thepower to idle and hold the elevator control back firmlyso the seaplane settles onto the water with no furtherinstability. Never try to “chase” the oscillations, as thisusually makes them worse and results in an accident.

Pilots must learn and practice the correct pitch attitudesfor takeoff, planing, and landing for each type of sea-plane until there is no doubt as to the proper angles forthe various maneuvers. The upper and lower limits ofthese pitch angles are established by the design of theseaplane; however, changing the seaplane’s grossweight, wing flap position, or center of gravity locationalso changes these limits. Increased weight increasesthe displacement of the floats or hull and raises thelower limit considerably. Extending the wing flaps fre-quently trims the seaplane to the lower limit at lowerspeeds, and may lower the upper limit at high speeds. Aforward center of gravity increases the possibility ofhigh angle porpoising, especially during landing.

SKIPPINGSkipping is a form of instability that may occur whenlanding at excessive speed with the nose at too high apitch angle. This nose-up attitude places the seaplane atthe upper trim limit of stability and causes the seaplaneto enter a cyclic oscillation when touching the water,which results in the seaplane skipping across the sur-face. This action is similar to skipping flat stones acrossthe water. Skipping can also occur by crossing a boatwake while taxiing on the step or during a takeoff.Sometimes the new seaplane pilot confuses a skip witha porpoise, but the pilot’s body sensations can quicklydistinguish between the two. A skip gives the body ver-tical “G” forces, similar to bouncing a landplane.Porpoising is a rocking chair type forward and aftmotion feeling.

To correct for skipping, first increase back pressure on theelevator control and add sufficient power to prevent thefloats from contacting the water. Then establish the properpitch attitude and reduce the power gradually to allow theseaplane to settle gently onto the water. Skippingoscillations do not tend to increase in amplitude, as inporpoising, but they do subject the floats and airframeto unnecessary pounding and can lead to porpoising.

TAKEOFFSA seaplane takeoff may be divided into four distinctphases: (1) The displacement phase, (2) the hump orplowing phase, (3) the planing or on the step phase, and(4) the lift-off.

The displacement phase should be familiar from thetaxiing discussion. During idle taxi, the displacementof water supports nearly all of the seaplane’s weight.The weight of the seaplane forces the floats down intothe water until a volume that weighs exactly as muchas the seaplane has been displaced. The surface area ofthe float below the waterline is called the wetted area,and it varies depending on the seaplane’s weight. Anempty seaplane has less wetted area than when it isfully loaded. Wetted area is a major factor in the cre-ation of drag as the seaplane moves through the water.

As power is applied, the floats move faster through thewater. The water resists this motion, creating drag. Theforward portion of the float is shaped to transform thehorizontal movement through the water into an upwardlifting force by diverting the water downward.Newton’s Third Law of Motion states that for everyaction, there is an equal and opposite reaction, and inthis case, pushing water downward results in anupward force known as hydrodynamic lift.

In the plowing phase, hydrodynamic lift begins push-ing up the front of the floats, raising the seaplane’s noseand moving the center of buoyancy aft. This, combinedwith the downward pressure on the tail generated byholding the elevator control all the way back, forcesthe rear part of the floats deeper into the water. Thiscreates more wetted area and consequently more drag,and explains why the seaplane accelerates so slowlyduring this part of the takeoff.

This resistance typically reaches its peak just beforethe floats are placed into a planing attitude. Figure 4-14shows a graph of the drag forces at work during a sea-plane takeoff run. The area of greatest resistance isreferred to as the hump because of the shape of thewater drag curve. During the plowing phase, theincreasing water speed generates more and morehydrodynamic lift. With more of the weight supportedby hydrodynamic lift, proportionately less is supportedby displacement and the floats are able to rise in thewater. As they do, there is less wetted area to causedrag, which allows more acceleration, which in turnincreases hydrodynamic lift. There is a limit to how farthis cycle can go, however, because as speed builds, sodoes the amount of drag on the remaining wetted area.Drag increases as the square of speed, and eventuallydrag forces would balance the power output of theengine and the seaplane would continue along the sur-face without further acceleration.

Seaplanes have been built with sufficient power toaccelerate to takeoff speed this way, but fortunately thestep was invented, and it makes further accelerationpossible without additional power. After passing overthe hump, the seaplane is traveling fast enough that itsweight can be supported entirely by hydrodynamic lift.Relaxing the back pressure on the elevator controlallows the float to rock up onto the step, and lifts the

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rear portions of the floats clear of the water. This elim-inates all of the wetted area aft of the step, along withthe associated drag.

As further acceleration takes place, the flight controlsbecome more responsive, just as in a landplane.Elevator deflection is gradually reduced to hold therequired planing attitude. As the seaplane continues toaccelerate, more and more weight is being supportedby the aerodynamic lift of the wings and waterresistance continues to decrease. When all of theweight is transferred to the wings, the seaplanebecomes airborne.

Several factors greatly increase the water drag orresistance, such as heavy loading of the seaplane orglassy water conditions. In extreme cases, the drag mayexceed the available thrust and prevent the seaplanefrom becoming airborne. This is particularly true whenoperating in areas with high density altitudes (high ele-vations/high temperatures) where the engine cannotdevelop full rated power. For this reason the pilot shouldpractice takeoffs using only partial power to simulatethe longer takeoff runs needed when operating wherethe density altitude is high and/or the seaplane is heavilyloaded. This practice should be conducted under thesupervision of an experienced seaplane instructor, and inaccordance with any cautions or limitations in theAFM/POH. Plan for the additional takeoff area required,as well as the flatter angle of climb after takeoff, andallow plenty of room for error.

Use all of the available cues to verify the wind direc-tion. Besides reading the water, pick up clues to thewind’s direction from wind indicators and streamerson the masts of moored boats, flags on flagpoles, orrising smoke. A boat moored to a buoy points into thewind, but be aware that it may have a stern anchor aswell, preventing it from pointing into the wind.

Waterfowl almost always align themselves facing intothe wind.

Naturally, be sure you have enough room for takeoff.The landing distance of a seaplane is much shorter thanthat required for takeoff, and many pilots have landedin areas that have turned out to be too short for takeoff.If you suspect that the available distance may be inad-equate, consider reducing weight by leaving some ofyour load behind or wait for more favorable weatherconditions. A takeoff that would be dangerous on a hot,still afternoon might be accomplished safely on the fol-lowing morning, with cooler temperatures and a briskwind.

In addition to wind, consider the effects of the currentwhen choosing the direction for takeoff. Keep in mindthat when taxiing in the same direction as the current,directional control may be reduced because the seaplaneis not moving as quickly through the water. In rivers ortidal flows, make crosswind or calm wind takeoffs in thesame direction as the current. This reduces the waterforces on the floats. Suppose the seaplane lifts off at 50knots and the current is 3 knots. If winds are calm, theseaplane needs a water speed of 47 knots to take offdownstream, but must accelerate to a water speed of 53knots to become airborne against the current. This dif-ference of 6 knots requires a longer time on the waterand generates more stress on the floats. The situationbecomes more complex when wind is a factor. If thewind is blowing against the current, its speed can helpthe wings develop lift sooner, but will raise higherwaves on the surface. If the wind is in the same directionas the current, at what point does the speed of the windmake it more worthwhile to take off against the current?In the previous example, a wind velocity of 3 knotswould exactly cancel the benefit of the current, since theair and water would be moving at the same speed. Inmost situations, take off into the wind if the speed of thewind is greater than the current.

Unlike landplane operations at airports, many otheractivities are permitted in waters where seaplaneoperations are conducted. Seaplane pilots encounter avariety of objects on the water, some of which arenearly submerged and difficult to see. These includeitems that are stationary, such as pilings and buoys,and those that are mobile, like logs, swimmers, waterskiers, and a variety of watercraft. Before beginningthe takeoff, it is a good practice to taxi along theintended takeoff path to check for any hazardousobjects or obstructions.

Make absolutely sure the takeoff path ahead is freeof boats, swimmers, and other water traffic, and besure it will remain so for the duration of the takeoffrun. Powerboats, wind-surfers, and jet-skis canmove quickly and change direction abruptly. As the

PO

UN

DS

TH

RU

ST

OR

DR

AG

KNOTS 20 40 60 80

"Hump"

WaterDrag

PropellerThrust

Figure 4-14. This graph shows water drag and propellerthrust during a takeoff run.

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seaplane’s nose comes up with the application of fullpower, the view ahead may be completely blocked bythe cowling. Check to the sides and behind the sea-plane as well as straight ahead, since many watercraftmove much faster than the normal taxi speed and maybe passing the seaplane from behind. In addition to thevessels themselves, also scan for their wakes and try toanticipate where the wakes will be during takeoff.Operators of motorboats and other watercraft often donot realize the hazard caused by moving their vesselsacross the takeoff path of a seaplane. It is usually betterto delay takeoff and wait for the swells to pass ratherthan encountering them at high speed. Even smallswells can cause dangerous pitching or rolling for aseaplane, so taxi across them at an angle rather thanhead-on. Remember to check for other air traffic andmake any appropriate radio calls.

Be sure to use the pre-takeoff checklist on every take-off. All checks are performed as the seaplane taxies,including the engine runup. Hold the elevator controlall the way back throughout the runup to minimizespray around the propeller. If there is significant wind,let the seaplane turn into the wind for the runup. Asr.p.m. increases, the nose rises into the plowing posi-tion and the seaplane begins to accelerate. Since this isa relatively unstable position, performing the runupinto the wind minimizes the possibility of crosswinds,rough water, or gusts upsetting the seaplane. Waste notime during the runup checks, but be thorough and pre-cise. Taxi speed will drop as soon as the power isreduced.

Water rudders are normally retracted before applyingtakeoff power. The buffeting and dynamic water pres-sure during a takeoff can cause serious damage if thewater rudders are left down.

As full power is applied during takeoff in most sea-planes, torque and P-factor tend to force the left floatdown into the water. Right rudder pressure helps tomaintain a straight takeoff path. In some cases, leftaileron may also help to counter the tendency to turnleft at low speeds, by increasing drag on the right sideof the seaplane.

Density altitude is particularly important in seaplaneflying. High, hot, and humid conditions reduce enginepower and propeller efficiency, and the seaplane mustalso attain a higher water speed in order to generate thelift required for takeoff. This increase in water speedmeans overcoming additional water drag. All of thesefactors combine to increase takeoff distances anddecrease climb performance. In high density altitudeconditions, consider not only the length of the waterrun, but the room required for a safe climbout as well.

The land area around a body of water is invariablysomewhat higher than the water surface. Tall trees arecommon along shorelines, and in many areas, steep ormountainous terrain rises from the water’s edge. Becertain the departure path allows sufficient room forsafe terrain clearance or for a wide climbing turn backover the water.

There are specific takeoff techniques for differentwind and water situations. Large water areas almostalways allow a takeoff into the wind, but there areoccasionally circumstances where a crosswind ordownwind takeoff may be more appropriate. Over theyears, techniques have evolved for handling roughwater or a glassy smooth surface. Knowing and prac-ticing these techniques not only keep skills polished sothey are available when needed, they also increaseoverall proficiency and add to the enjoyment ofseaplane flying.

NORMAL TAKEOFFSMake normal takeoffs into the wind. Once the winddirection is determined and the takeoff path chosen,configure the seaplane and perform all of the pre-take-off checks while taxiing to the takeoff position. Verifythat the takeoff will not interfere with other traffic,either on the water’s surface or in the air.

Hold the elevator control all the way back and apply fullpower smoothly and quickly, maintaining directionalcontrol with the rudder. When the nose reaches its highestpoint, ease the back pressure to allow the seaplane tocome up on the step. Establish the optimum planing atti-tude and allow the seaplane to accelerate to lift-off speed.In most cases, the seaplane lifts off as it reaches flyingspeed. Occasionally it may be necessary to gently helpthe floats unstick by either using some aileron to lift onefloat out of the water or by adding a small amount of backpressure on the elevator control. Once off the water, theseaplane accelerates more quickly. When a safe airspeedis achieved, establish the pitch attitude for the best rate ofclimb (VY) and complete the climb checklist. Turn asnecessary to avoid overflying noise-sensitive areas, andreduce power as appropriate to minimize noise.

CROSSWIND TAKEOFFSIn restricted or limited areas such as canals or narrowrivers, it is not always possible to take off or landdirectly into the wind. Therefore, acquiring skill incrosswind techniques enhances the safety of seaplaneoperation. Crosswinds present special difficulties forseaplane pilots. The same force that acts to lift theupwind wing also increases weight on the downwindfloat, forcing it deeper into the water and increasingdrag on that side. Keep in mind that the allowablecrosswind component for a floatplane may be signifi-cantly less than for the equivalent landplane.

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A crosswind has the same effect on a seaplane duringtakeoff as on a landplane, that is, it tends to push theseaplane sideways across the takeoff path, whichimposes side loads on the landing gear. In addition,wind pressure on the vertical tail causes the seaplane totry to weathervane into the wind.

At the beginning of the takeoff roll in a landplane, driftand weathervaning tendencies are resisted by the fric-tion of the tires against the runway, usually assisted bynosewheel steering, or in some cases even differentialbraking. The objective in a crosswind takeoff is thesame in landplanes and seaplanes: to counteract driftand minimize the side loads on the landing gear.

The sideways drifting force, acting through the sea-plane’s center of gravity, is opposed by the resistance ofthe water against the side area of the floats. This createsa force that tends to tip the seaplane sideways, pushingthe downwind float deeper into the water and lifting theupwind wing. The partly submerged float has even moreresistance to sideways motion, and the upwind wing dis-plays more vertical surface area to the wind, intensifyingthe problem. Without intervention by the pilot, this tip-ping could continue until the seaplane capsizes.

During a takeoff in stiff crosswinds, weathervaningforces can cause an uncontrolled turn to begin. As theturn develops, the addition of centrifugal force actingoutward from the turn aggravates the problem. The keelsof the floats resist the sideways force, and the upwindwing tends to lift. If strong enough, the combination ofthe wind and centrifugal force may tip the seaplane tothe point where the downwind float submerges and

subsequently the wingtip may strike the water. This isknown as a waterloop, and the dynamics are similar to agroundloop on land. Although some damage occurswhen the wingtip hits the ground during a groundloop,the consequences of plunging a wingtip underwater in aseaplane can be disastrous. In a fully developed water-loop, the seaplane may be severely damaged or maycapsize. Despite these dire possibilities, crosswind take-offs can be accomplished safely by exercising goodjudgment and proper piloting technique.

Since there are no clear reference lines for directionalguidance, such as those on airport runways, it can bedifficult to quickly detect side drift on water. Wavesmay make it appear that the water is moving sideways,but remember that although the wind moves the waves,the water remains nearly stationary. The waves aresimply an up-and-down motion of the water surface—the water itself is not moving sideways. To maintain astraight path through the water, pick a spot on the shoreas an aim point for the takeoff run. On the other hand,some crosswind techniques involve describing acurved path through the water. Experience will helpdetermine which technique is most appropriate for agiven situation.

CONTROLLED WEATHERVANINGIn light winds, it is easy to counteract the weathervan-ing tendency during the early part of the takeoff run bycreating an allowance for it from the beginning. Priorto adding takeoff power, use the water rudders to set upa heading somewhat downwind of the aim point. Theangle will depend on the speed of the wind—the higher

Begin Takeoff byAiming Downwind of the Intended Takeoff Path

AirplaneWeathervanes toIntended PathDuring Takeoff Run

Intended Takeoff Path

Figure 4-15. Anticipate weathervaning by leading the aim point, setting up a somewhat downwind heading prior to starting thetakeoff. Choose an aim point that does not move, such as a buoy or a point on the far shore.

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the wind, the greater the lead angle. Create just enoughof a lead angle so that when the water rudders are raisedand power is applied, the seaplane weathervanes to thedesired heading during the time it gains enough speedto make the air rudder and ailerons effective. As theseaplane transitions to the plowing attitude, the weath-ervaning tendency decreases as the fronts of the floatscome out of the water, adding vertical surface area atthe front of the seaplane. Use full aileron into the windas the takeoff run begins, and maintain enough aileronto keep the upwind wing from lifting as airspeed builds.[Figure 4-15 on previous page]

USING WATER RUDDERSAnother technique for maintaining a straight takeoffpath involves leaving the water rudders down to assistwith steering. Using the water rudders provides addeddirectional control until the aerodynamic controlsbecome effective.

To use this technique, align the seaplane with the aimpoint on the shore, hold full aileron into the wind, andapply takeoff power. As the seaplane accelerates, useenough aileron pressure to keep the upwind wingdown. The downwind float should lift free of the waterfirst. After lift-off, make a coordinated turn to establishthe proper crab angle for the climb, and retract thewater rudders.

This takeoff technique subjects the water rudders tohigh dynamic water pressures and could cause damage.Be sure to comply with the advice of the float manu-facturer. [Figure 4-16]

DOWNWIND ARCThe other crosswind takeoff technique results in acurved path across the water, starting somewhat into thewind and turning gradually downwind during the takeoffrun. This reduces the actual crosswind component at thebeginning of the takeoff, when the seaplane is most sus-ceptible to weathervaning. As the aerodynamic controlsbecome more effective, the pilot balances the side loadsimposed by the wind with the skidding force of an inten-tional turn, as always, holding the upwind wing downwith the ailerons. [Figure 4-17]

The pilot plans a curved path and follows this arc toproduce sufficient centrifugal force so that the seaplanetends to lean outward against the wind force. Duringthe run, the pilot can adjust the rate of turn by varyingrudder pressure, thereby increasing or decreasing thecentrifugal force to compensate for a changing windforce. In practice, it is quite simple to plan sufficientcurvature of the takeoff path to cancel out strongcrosswinds, even on very narrow rivers. Note that the

tightest part of the downwind arc is when the seaplaneis traveling at slower speeds.

The last portion of a crosswind takeoff is somewhatsimilar to a landplane. Use ailerons to lift the down-wind wing, providing a sideways component of lift tocounter the effect of the crosswind. This means that thedownwind float lifts off first. Be careful not to drop theupwind wing so far that it touches the water. Whenusing a straight takeoff path, keep the nose on the aimpoint with opposite rudder and maintain the proper stepattitude until the other float lifts off. Unlike a land-plane, there is usually no advantage in holding the sea-plane on the water past normal lift-off speed, and doingso may expose the floats to unnecessary pounding asthey splash through the waves. Once airborne, make acoordinated turn to the crab angle that results in astraight track toward the aim point, and pitch to obtainthe desired climb airspeed.

Again, experience plays an important part in successfuloperation during crosswinds. It is essential that all sea-plane pilots have thorough knowledge and skill in thesemaneuvers.

DOWNWIND TAKEOFFSDownwind takeoffs in a seaplane present a somewhatdifferent set of concerns. If the winds are light, thewater is smooth, and there is plenty of room, a down-wind takeoff may be more convenient than a longdownwind taxi to a position that would allow a takeoffinto the wind. In any airplane, the wing needs to attaina specific airspeed in order to fly, and that indicatedairspeed is the same regardless of wind direction.

Start Takeoff Run with WaterRudders Down.

Retract Water RuddersAfter Lift-Off.

Continue Takeoff UsingAppropriate Aerodynamic

Controls

Figure 4-16. Remember to retract the water rudders aftertakeoff to avoid damage during the next landing.

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However, when taking off downwind, obtaining theairspeed means accelerating to a proportionately highergroundspeed. Naturally, the takeoff run is longerbecause the wings must first be accelerated to the speedof the wind, then accelerated to the correct airspeed togenerate the lift required for takeoff. So far, this isidentical to what occurs with a landplane during adownwind takeoff. But in addition, a downwind takeoffrun in a seaplane is further lengthened by the factor offloat drag. The speed of the floats in the water correspondsto the higher groundspeed required in a landplane, but thedrag of the floats increases as the square of their speed.This increase in drag is much greater than the increasein rolling resistance of tires and wheel bearings in alandplane. A tailwind may lengthen the seaplane’stakeoff distance much more dramatically than the sametailwind in a landplane.

Nevertheless, there are situations in which a downwindtakeoff may be more favorable than taking off into thewind. If there is a long lake with mountains at theupwind end and a clear departure path at the other, adownwind takeoff might be warranted. Likewise, noiseconsiderations and thoughtfulness might prompt adownwind takeoff away from a populated shore area ifplenty of water area is available. In areas where thecurrent favors a downwind takeoff, the advantagegained from the movement of the water can more thancompensate for the wind penalty. Keep in mind thatovercoming the current creates far more drag thanaccelerating a few extra knots downwind with the cur-rent. In all cases, safety requires a thorough knowledgeof the takeoff performance of the seaplane.

GLASSY WATER TAKEOFFSGlassy water makes takeoff more difficult in twoways. The smoothness of the surface has the effect ofincreasing drag, making acceleration and lift-offmore difficult. This can feel as if there is suctionbetween the water and the floats. A little surfaceroughness actually helps break the contact betweenthe floats and the water by introducing turbulence andair bubbles between water and the float bottoms. Theintermittent contact between floats and water at themoment of lift-off cuts drag and allows the seaplaneto accelerate while still obtaining some hydrody-namic lift, but glassy water maintains a continuousdrag force. Once airborne, the lack of visual cues tothe seaplane’s height above the water can create apotentially dangerous situation unless a positive rateof climb is maintained.

The takeoff technique is identical to a normal takeoffuntil the seaplane is on the step and nearly at flyingspeed. At this point, the water drag may prevent theseaplane from accelerating the last few knots to lift-offspeed. To reduce float drag and break the grip of thewater, the pilot applies enough aileron pressure to liftone float just out of the water and allows the seaplaneto continue to accelerate on the step of the other floatuntil lift-off. By allowing the seaplane to turn slightlyin the direction the aileron is being held rather thanholding opposite rudder to maintain a straight course,considerable aerodynamic drag is eliminated, aidingacceleration and lift-off. When using this technique, becareful not to lift the wing so much that the oppositewing contacts the water. Obviously, this would haveserious consequences. Once the seaplane lifts off,establish a positive rate of climb to prevent inadver-tently flying back into the water.

Another technique that aids glassy water takeoffsentails roughening the surface a little. By taxiingaround in a circle, the wake of the seaplane spreads andreflects from shorelines, creating a slightly roughersurface that can provide some visual depth and helpthe floats break free during takeoff.

Occasionally a pilot may have difficulty getting theseaplane onto the step during a glassy water takeoff,particularly if the seaplane is loaded to its maximumauthorized weight. The floats support additionalweight by displacing more water; they sink deeper intothe water when at rest. Naturally, this wets more sur-face area, which equates to increased water drag whenthe seaplane begins moving, compared to a lightlyloaded situation. Under these conditions the seaplanemay assume a plowing position when full power isapplied, but may not develop sufficient hydrodynamiclift to get on the step due to the additional water drag.The careful seaplane pilot always plans ahead and con-siders the possibility of aborting the takeoff.

Centrifugal Force

Figure 4-17.The downwind arc balances wind force with cen-trifugal force.

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Nonetheless, if these conditions are not too excessive,the takeoff often can be accomplished using thefollowing technique.

After the nose rises to the highest point in the plowingposition with full back elevator pressure, decrease backpressure somewhat. The nose will drop if the seaplanehas attained enough speed to be on the verge of attain-ing the step position. After a few seconds, the nose willrise again. At the instant it starts to rise, reinforce therise by again applying firm back pressure. As soon asthe nose reaches its maximum height, repeat the entireroutine. After several repetitions, the nose attainsgreater height and speed increases. If the elevator controlis then pushed well forward and held there, the seaplanewill slowly flatten out on the step and the controls maythen be eased back to the neutral position. Once on thestep, the remainder of the takeoff run follows the usualglassy water procedure.

ROUGH WATER TAKEOFFSThe objective in a rough water takeoff is similar to thatof a rough or soft field takeoff in a landplane: to transferthe weight of the airplane to the wings as soon as possi-ble, get airborne at a minimum airspeed, accelerate inground effect to a safe climb speed, and climb out.

In most cases an experienced seaplane pilot can safelytake off in rough water, but a beginner should notattempt to take off if the waves are too high. Using theproper procedure during rough water operation lessensthe abuse of the floats, as well as the entire seaplane.

During rough water takeoffs, open the throttle to take-off power just as the floats begin rising on a wave. Thisprevents the float bows from digging into the water andhelps keep the spray away from the propeller. Apply alittle more back elevator pressure than on a smoothwater takeoff. This raises the nose to a higher angleand helps keep the float bows clear of the water.

Once on the step, the seaplane can begin to bouncefrom one wave crest to the next, raising its nose higherwith each bounce, so each successive wave is struckwith increasing severity. To correct this situation andto prevent a stall, smooth elevator pressures should beused to set up a fairly constant pitch attitude that allowsthe seaplane to skim across each successive wave asspeed increases. Maintain control pressure to preventthe float bows from being pushed under the water sur-face, and to keep the seaplane from being thrown intothe air at a high pitch angle and low airspeed.Fortunately, a takeoff in rough water is generallyaccomplished within a short time because if there issufficient wind to make water rough, the wind is alsostrong enough to produce aerodynamic lift earlier andenable the seaplane to become airborne quickly.

The relationship of the spacing of the waves to thelength of the floats is very important. If the wavelength

is less than half the length of the floats, the seaplane isalways supported by at least two waves at a time. Ifthe wavelength is longer than the floats, only one waveat a time supports the seaplane. This creates dangerouspitching motions, and takeoff should not be attemptedin this situation.

With respect to water roughness, consider the effect ofa strong water current flowing against the wind. If thecurrent is moving at 10 knots and the wind is blowingthe opposite direction at 15 knots, the relative velocitybetween the water and the wind is 25 knots, and thewaves will be as high as those produced in still waterby a wind of 25 knots.

The advisability of canceling a proposed flight becauseof rough water depends on the size of the seaplane, wingloading, power loading, and, most importantly, thepilot’s ability. As a general rule, if the height of thewaves from trough to crest is more than half the heightof the floats from keel to deck, takeoffs should not beattempted except by expert seaplane pilots. Chapter 8,Emergency Open Sea Operations, contains moreinformation on rough water operations.

CONFINED AREA TAKEOFFSIf operating from a small body of water, an acceptabletechnique may be to begin the takeoff run whileheaded downwind, and then turning to complete thetakeoff into the wind. This may be done by putting theseaplane on the step while on a downwind heading,then making a step turn into the wind to complete thetakeoff. Exercise caution when using this techniquesince wind and centrifugal force are acting in the samedirection and could result in the seaplane tipping over.The water area must be large enough to permit a widestep turn, and winds should be light.

In some cases, the water area may be adequate butsurrounding high terrain creates a confined area. Theterrain may also block winds, resulting in a glassywater situation as well. Such conditions may lead toa dangerous situation, especially when combined witha high density altitude. Even though landing was notdifficult, careful planning is necessary for the takeoff. Ifthe departure path leads over high terrain, consider cir-cling back over the water after takeoff to gain altitude. Ifair temperatures have increased since landing, make theproper allowance for reduced takeoff performance dueto the change in density altitude. Think about spendingthe night to take advantage of cooler temperatures thenext morning. Although the decision may be difficult,consider leaving some cargo or passengers behind iftakeoff safety is in question. It is far better to make asecond trip to pick them up than to end your takeoff inthe trees along the shore.

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PERFORMANCE CONSIDERATIONSFOR TAKEOFF, CLIMB, CRUISE, ANDLANDINGSince many pilots are accustomed to a certain level ofperformance from a specific make and model of landairplane, the changes in performance when that sameairplane is equipped with floats can lead to trouble fora careless or complacent pilot. Floats weigh somewhatmore than the wheeled landing gear they replace, butfloats are designed to produce aerodynamic lift to off-set some of the weight penalty. Generating liftinevitably creates induced drag, which imposes a smallreduction in overall performance. By far the greatestimpact on performance comes from the parasitic dragof the floats.

TAKEOFFIn a landplane, takeoff distance increases with addi-tional takeoff weight for two reasons: it takes longerfor the engine and propeller to accelerate the greatermass to lift-off speed, and the lift-off speed itself ishigher because the wings must move faster to producethe extra lift required. For seaplanes, there are twomore factors, both due to water drag. As seaplaneweight increases, the floats sink deeper into the water,creating more drag during initial acceleration. As withthe landplane, the seaplane must also accelerate to ahigher airspeed to generate more lift, but the seaplanemust overcome significantly more water drag force asspeed increases. This extra drag reduces the rate ofacceleration and results in a longer takeoff run.

Naturally, the location of the additional weight withinthe seaplane affects center of gravity (CG) location.Because of the way the floats respond to weight, theCG location affects the seaplane’s handling charac-teristics on the water. If the CG is too far aft, it maybe impossible to put the seaplane on the step. If theCG is located to one side of the centerline, one floatwill be pushed deeper into the water, resulting inmore water drag on that side. Be sure to balance thefuel load between left and right wing tanks, and payattention to how baggage or cargo is secured, so thatthe weight is distributed somewhat evenly from sideto side. [Figure 5-1]

The importance to weight and balance of pumping outthe float compartments should be obvious. Waterweighs 8.34 pounds per gallon, or a little over 62pounds per cubic foot. Performance decreases when-ever the wings and engine have to lift and carry uselesswater in a float compartment. Even a relatively smallamount of water in one of the front or rear float com-partments could place the airplane well outside of CGlimits and seriously affect stability and control.Naturally, water also moves around in response tochanges in attitude, and the sloshing of water in thefloats can create substantial CG changes as the sea-plane is brought onto the step or rotated into a climbattitude.

Some pilots use float compartments near the CG tostow iced fish or game from hunting expeditions. It isimperative to adhere to the manufacturer’s weight andbalance limitations and to include the weight andmoment of float compartment contents in weight andbalance calculations.

Density altitude is a very important factor in seaplanetakeoff performance. High altitudes, high tempera-tures, high humidity, and even low barometric pressurecan combine to rob the engine and propeller of thrustand the wings of lift. Seaplane pilots are encouragedto occasionally simulate high density altitude byusing a reduced power setting for takeoff. This exer-cise should only be attempted where there is plentyof water area, as the takeoff run will be much longer.An experienced seaplane instructor can assist withchoosing an appropriate power setting and demon-strating proper technique.

Unbalanced Fuel Load

Figure 5-1. The location of the CG can affect seaplanehandling.

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CLIMB AND CRUISEWhen comparing the performance of an airplane withwheels to the same airplane equipped with floats, thedrag and weight penalty of the floats usually results ina reduced climb rate for any given weight. Likewise,cruise speeds will usually be a little lower for a partic-ular power setting. This in turn means increased fuelconsumption and reduced range. Unless the airplanewas originally configured as a seaplane, the perform-ance and flight planning information for a landplaneconverted to floats will typically be found in theSupplements section rather than the Performance sec-tion of the Airplane Flight Manual (AFM) or Pilot’sOperating Handbook (POH).

In addition to working within the limits of the sea-plane’s range, the pilot planning a cross-country flightmust also consider the relative scarcity of refuelingfacilities for seaplanes. Amphibians have access to landairports, of course, but seaplanes without wheels needto find water landing facilities that also sell aviationfuel. While planning the trip, it is wise to call ahead toverify that the facilities have fuel and will be open atthe intended arrival times. The Seaplane PilotsAssociation publishes a Water Landing Directory thatis very helpful in planning cross-country flights.

In flight, the seaplane handles very much like the cor-responding landplane. On many floatplanes, the floatsdecrease directional stability to some extent. The floatstypically have more vertical surface area ahead of theairplane’s CG than behind it. If the floats remainaligned with the airflow, this causes no problems, but ifthe airplane begins to yaw or skid, this vertical area actssomewhat like a large control surface that tends toincrease the yaw, making the skid worse. [Figure 5-2]Additional vertical surface well behind the CG cancounteract the yaw force created by the front of thefloats, so many floatplanes have an auxiliary finattached to the bottom of the tail, or small vertical sur-faces added to the horizontal stabilizer. [Figure 5-3]

LANDINGLandplane pilots are trained to stay on the lookout forgood places to land in an emergency, and to be able toplan a glide to a safe touchdown should the engine(s)fail. An airplane equipped with floats will usually havea steeper power-off glide than the same airplane withwheels. This means a higher rate of descent and adiminished glide range in the event of an engine fail-ure, so the pilot should keep this in mind when spottingpotential landing areas during cruising flight.

Seaplanes often permit more options in the event of anunplanned landing, since land can be used as well aswater. While a water landing may seem like the onlychoice for a non-amphibious seaplane, a smoothlanding on grass, dirt, or even a hard-surface runwayusually causes very little damage to the floats or hull,and may frequently be the safer alternative.

Figure 5-2. The side area of the floats can decrease direc-tional stability.

Figure 5-3. Vertical surfaces added to the tail help restoredirectional stability.

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The most extreme pitch force logically results from asudden engine failure, when the full thrust of theengine and its associated downward pitching force aresuddenly removed. Forward thrust is replaced by thedrag of a windmilling propeller, which adds a newupward pitching force. Since the seaplane is alreadytrimmed with a considerable elevator force to coun-teract the downward pitch force of the engine, thenose pitches up abruptly. If this scenario occurs justafter takeoff, when the engine has been producingmaximum power, airspeed is low, and there is littlealtitude, the pilot must react instantly to overpowerthe upward pitching forces and push the nose down toavoid a stall.

The reversal of typical pitch forces also comes intoplay if porpoising should begin during a takeoff. Asdiscussed in Chapter 4, Seaplane Operations -Preflight and Takeoffs, porpoising usually occurswhen the planing angle is held too low by the pilot,forcing the front portion of the floats to drag until awave builds up and travels back along the float. Thesame thing can happen with the hull of a flying boat,and the nose-down force of a high thrust line can makeporpoising more likely. Once porpoising develops, thestandard solution is to reduce power and let the air-plane settle back into the water. But if power isreduced too quickly in a seaplane with a high-mountedengine, the sudden upward pitching force can combinewith the porpoising to throw the seaplane into the airwith inadequate airspeed for flight, decreasing thrust,and inadequate altitude for recovery.

Depending on how far the engine is from the airplane’sCG, the mass of the engine can have detrimentaleffects on roll stability. Some seaplanes have theengine mounted within the upper fuselage, while oth-

FLIGHT CHARACTERISTICS OFSEAPLANES WITH HIGH THRUST LINESMany of the most common flying boat designs havethe engine and propeller mounted well above the air-frame’s CG. This results in some unique handlingcharacteristics. The piloting techniques necessary tofly these airplanes safely are not intuitive and must belearned. Any pilot transitioning to such an airplane isstrongly urged to obtain additional training specific tothat model of seaplane.

Designing a seaplane with the engine and propellerhigh above the water offers some important advan-tages. The propeller is out of the spray during takeoffsand landings, and more of the fuselage volume can beused for passengers and cargo. The pilot usually sitswell forward of the wing, and enjoys an excellent viewin almost every direction.

Pilots who fly typical light twins are familiar with whathappens when one engine is producing power and theother is not. The airplane tends to yaw toward the deadengine. This happens because the thrust line is locatedsome distance from the airplane’s CG. In somerespects, this situation is similar to the single-engineseaplane with a high thrust line, except that the sea-plane flies on one engine all the time. When power isapplied, the thrust tends to pitch the nose down, and aspower is reduced, the nose tends to rise. [Figure 5-4]This is exactly the opposite of what most pilots areaccustomed to. In typical airplanes, including mostfloatplanes, applying power raises the nose and initi-ates a climb.

Naturally the magnitude of these pitch forces is pro-portional to how quickly power is applied or reduced.

Figure 5-4. Pitching forces in seaplanes with a high thrust line.

Increasing Thrust

Decreasing Thrust

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ers have engines mounted on a pylon well above themain fuselage. If it is far from the CG, the engine canact like a weight at the end of a lever, and once startedin motion it tends to continue in motion. Imaginebalancing a hammer upright with the handle on thepalm of the hand. [Figure 5-5]

Finally, seaplanes with high-mounted engines mayhave unusual spin characteristics and recovery tech-niques. These factors reinforce the point that pilotsneed to obtain thorough training from a qualified

instructor in order to operate this type of seaplanesafely.

MULTIENGINE SEAPLANESA rating to fly single-engine seaplanes does not entitlea pilot to fly seaplanes with two or more engines. The

addition of a multiengine sea rating to a pilotcertificate requires considerable additional training.Dealing with engine failures and issues of asymmetri-cal thrust are important aspects in the operation ofmultiengine seaplanes.

Figure 5-5. Roll instability with a high-mounted engine.

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LANDING AREA RECONNAISSANCEAND PLANNINGWhen a landplane makes an approach at a towered air-port, the pilot can expect that the runway surface willbe flat and free of obstructions. Wind information andlanding direction are provided by the tower. In wateroperations, the pilot must make a number of judgmentsabout the safety and suitability of the landing area,evaluate the characteristics of the water surface, deter-mine wind direction and speed, and choose a landingdirection. It is rare for active airport runways to beused by other vehicles, but common for seaplane pilotsto share their landing areas with boats, ships, swim-mers, jet-skis, wind-surfers, or barges, as well as otherseaplanes.

It is usually a good practice to circle the area ofintended landing and examine it thoroughly forobstructions such as pilings or floating debris, and tonote the direction of movement of any boats that maybe in or moving toward the intended landing site. Evenif the boats themselves will remain clear of the landingarea, look for wakes that could create hazardous swellsif they move into the touchdown zone. This is also thetime to look for indications of currents in movingwater. Note the position of any buoys marking pre-ferred channels, hidden dangers, or off-limits areassuch as no-wake zones or swimming beaches. Just as itis a good idea in a landplane to get a mental picture ofthe taxiway arrangement at an unfamiliar airport priorto landing, the seaplane pilot should plan a taxi routethat will lead safely and efficiently from the intendedtouchdown area to the dock or mooring spot. This isespecially important if there is a significant wind thatcould make turns difficult while taxiing or necessitatesailing backward or sideways to the dock. If the wateris clear, and there is not much wind, it is possible tosee areas of waterweeds or obstructions lying belowthe surface. Noting their position before landing canprevent fouling the water rudders with weeds whiletaxiing, or puncturing a float on a submerged snag. Inconfined areas, it is essential to verify before landingthat there is sufficient room for a safe takeoff under theconditions that are likely to prevail at the intendeddeparture time. While obstruction heights are regulatedin the vicinity of land airports and tall structures areusually well marked, this is not the case with most

water landing areas. Be alert for towers, cranes, powerlines,and the masts of ships and boats on the approach path.Finally, plan a safe, conservative path for a go-aroundshould the landing need to be aborted.

Most established seaplane bases have a windsock, butif one is not visible, there are many other cues to gaugethe wind direction and speed prior to landing. If thereare no strong tides or water currents, boats lying atanchor weathervane and automatically point into thewind. Be aware that some boats also set a stern anchor,and thus do not move with changes in wind direction.There is usually a glassy band of calm water on theupwind shore of a lake. Sea gulls and other waterfowlusually land into the wind and typically head into thewind while swimming on the surface. Smoke, flags,and the set of sails on sailboats also provide the pilotwith a fair approximation of the wind direction. If thereis an appreciable wind velocity, wind streaks parallel tothe wind form on the water. In light winds, they appearas long, narrow, straight streaks of smooth waterthrough the wavelets. In winds of approximately 10knots or more, foam accents the streaks, forming dis-tinct white lines. Although wind streaks show directionvery accurately, the pilot must still determine whichend of the wind streak is upwind. For example, an east-west wind streak could mean a wind from the east orthe west—it is up to the pilot to determine which.[Figure 6-1]

Figure 6-1. Wind streaks show wind direction accurately, butthe pilot must determine which end of the streak is upwind.

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If there are whitecaps or foam on top of the waves, thefoam appears to move into the wind. This illusion iscaused by the motion of the waves, which move morequickly than the foam. As the waves pass under thefoam, the foam appears to move in the opposite direc-tion. The shape of shorelines and hills influences winddirection, and may cause significant variations fromone area to another. Do not assume that because thewind is from a certain direction on this side of the lakethat it is from the same direction on the other side.

Except for glassy water, it is usually best to plan to landon the smoothest water available. When a swell systemis superimposed on a second swell system, some of thewaves may reinforce each other, resulting in higherwaves, while other waves cancel each other out, leav-ing smoother areas. Often it is possible to avoid thelarger waves and land on the smooth areas.

In seaplanes equipped with retractable landing gear(amphibians), it is extremely important to make certainthat the wheels are retracted when landing on water.Wherever possible, make a visual check of the wheelsthemselves, in addition to checking the landing gearposition indicators. A wheels-down landing on water isalmost certain to capsize the seaplane, and is far moreserious than landing the seaplane on land with thewheels up. Many experienced seaplane pilots make apoint of saying out loud to themselves before everywater landing, “This is a water landing, so the wheelsshould be up.” Then they confirm that each wheel is upusing externally mounted mirrors and other visual indi-cators. Likewise, they verbally confirm that the wheelsare down before every landing on land. The water rud-ders are also retracted for landings.

When planning the landing approach, be aware that theseaplane has a higher sink rate than its landplane coun-terpart at the same airspeed and power setting. Withsome practice, it becomes easy to land accurately on apredetermined spot. Landing near unfamiliar shore-

lines increases the possibility of encountering sub-merged objects and debris.

Besides being safe, it is also very important for sea-plane pilots to make a conscious effort to avoid inflict-ing unnecessary noise on other people in the area.Being considerate of others can often mean the differ-ence between a warm welcome and the banning offuture seaplane activity in a particular location. Theactions of one pilot can result in the closing of a desir-able landing spot to all pilots. People with houses alongthe shore of a lake usually include the quiet as one ofthe reasons they chose to live there. Sometimes highterrain around a lake or the local topography of a shore-line can reflect and amplify sound, so that a seaplanesounds louder than it would otherwise. A good practiceis to cross populated shorelines no lower than 1,000feet AGL whenever feasible. To the extent possibleconsistent with safety, avoid overflying houses duringthe landing approach. If making a go-around, turn backover the water for the climbout, and reduce powerslightly after attaining a safe altitude and airspeed. Areduction of 200 r.p.m. makes a significant differencein the amount of sound that reaches the ground.

LANDINGIn water landings, the major objectives are to touchdown at the lowest speed possible, in the correct pitchattitude, without side drift, and with full controlthroughout the approach, landing, and transition totaxiing.

The correct pitch attitude at touchdown in a landplanevaries between wide limits. For example, wheel land-ings in an airplane with conventional-gear, require anearly flat pitch attitude, with virtually zero angle ofattack, while a full-stall landing on a short field mightcall for a nose-high attitude. The touchdown attitudefor a seaplane typically is very close to the attitude fortaxiing on the step. The nose may be a few degreeshigher. The objective is to touch down on the steps,

Figure 6-2.The touchdown attitude for most seaplanes is almost the same as for taxiing on the step.

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contact the water in a nose-down attitude, driving thefloat bows underwater and capsizing the seaplane.Raising the flaps can help keep the seaplane firmly onthe water. To end the step taxi, close the throttle andgradually apply full up elevator as the seaplane slows.

CROSSWIND LANDINGLanding directly into the wind might not be practicaldue to water traffic in the area, obstructions on orunder the water, or a confined landing area, such as ariver or canal. In landing a seaplane with any degree ofcrosswind component, the objectives are the same aswhen landing a landplane: to minimize sideways driftduring touchdown and maintain directional controlafterward. Because floats have so much more side areathan wheels, even a small amount of drift at touchdowncan create large sideways forces. This is importantbecause enough side force can lead to capsizing. Also,the float hardware is primarily designed to take verticaland fore-and-aft loads rather than side loads.

If the seaplane touches down while drifting sideways,the sudden resistance as the floats contact the watercreates a skidding force that tends to push the down-wind float deeper into the water. The combination ofthe skidding force, wind, and weathervaning as theseaplane slows down can lead to a loss of directionalcontrol and a waterloop. If the downwind float sub-merges and the wingtip contacts the water when theseaplane is moving at a significant speed, the seaplanecould flip over. [Figure 6-3 on next page]

Floatplanes frequently have less crosswind componentcapability than their landplane counterparts.Directional control can be more difficult on waterbecause the surface is more yielding, there is less sur-face friction than on land, and seaplanes lack brakes.These factors increase the seaplane’s tendency toweathervane into the wind.

One technique sometimes used to compensate forcrosswinds during water operations is the same as thatused on land; that is, by lowering the upwind wingwhile holding a straight course with rudder. This cre-ates a slip into the wind to offset the drifting tendency.The apparent movement of the water’s surface duringthe landing approach can be deceiving. Wave motionmay make it appear that the water is moving sideways,but although the wind moves the waves, the wateritself remains virtually stationary. Waves are simplyan up-and-down motion of the water surface—thewater itself is not moving sideways. To detect sidedrift over water and maintain a straight path duringlanding, pick a spot on the shore or a stationary buoyas an aim point. Lower the upwind wing just enoughto stop any drift, and use rudder to maintain a straight

with the sterns of the floats near or touching the waterat the same time. [Figure 6-2] If the nose is muchhigher or lower, the excessive water drag puts unneces-sary stress on the floats and struts, and can cause thenose to pitch down, allowing the bows of the floats todig into the water. Touching down on the step keepswater drag forces to a minimum and allows energy todissipate more gradually.

NORMAL LANDINGMake normal landings directly into the wind.Seaplanes can be landed either power-off or power-on,but power-on landings are generally preferred becausethey give the pilot more positive control of the rate ofsink and the touchdown spot. To touch down at theslowest possible speed, extend the flaps fully. Useflaps, throttle, and pitch to control the glidepath andestablish a stabilized approach at the recommendedapproach airspeed. The techniques for glidepath con-trol are similar to those used in a landplane.

As the seaplane approaches the water’s surface,smoothly raise the nose to the appropriate pitch atti-tude for touchdown. As the floats contact the water,use gentle back pressure on the elevator control tocompensate for any tendency of the nose to drop.When the seaplane is definitely on the water, closethe throttle and maintain the touchdown attitude untilthe seaplane begins to come off the step. Once itbegins to settle into the plowing attitude, apply fullup elevator to keep the nose as high as possible andminimize spray hitting the propeller.

As the seaplane slows to taxi speed, lower the waterrudders to provide better directional control. Raise theflaps and perform the after-landing checklist.

The greater the speed difference between the seaplaneand the water, the greater the drag at touchdown, andthe greater the tendency for the nose to pitch down.This is why the touchdown is made at the lowest possi-ble speed for the conditions. Many landplane pilotstransitioning to seaplanes are surprised at the shortnessof the landing run, in terms of both time and distance.It is not uncommon for the landing run from touch-down to idle taxi to take as little as 5 or 6 seconds.

Sometimes the pilot chooses to remain on the step aftertouchdown. To do so, merely add sufficient power andmaintain the planing attitude immediately after touch-down. It is important to add enough power to preventthe seaplane from coming off the step, but not so muchthat the seaplane is close to flying speed. With too muchtaxi speed, a wave or swell could throw the seaplane intothe air without enough speed to make a controlledlanding. In that situation, the seaplane may stall and

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path. As the seaplane touches down on the upwindfloat, the water drag will quickly slow the seaplane andthe other float will touch down as aerodynamic liftdecreases. Close the throttle, and as the seaplane’sspeed dissipates, increase aileron to hold the upwindwing down. The seaplane is most unstable as it is com-ing off the step and transitioning through the plowingphase. Be ready for the seaplane to weathervane into thewind as the air rudder becomes less effective. Manypilots make a turn to the downwind side after landing tominimize weathervaning until the seaplane has slowedto taxi speed. Since the seaplane will weathervanesooner or later, this technique reduces the centrifugalforce on the seaplane by postponing weathervaning untilspeed has dissipated. Once the seaplane settles into thedisplacement attitude, lower the water rudders for betterdirectional control. [Figure 6-4]

Another technique used to compensate for crosswinds(preferred by many seaplane pilots) is the downwindarc method. Seaplanes need not follow a straight pathduring landing, and by choosing a curved path, the pilotcan create a sideward force (centrifugal force) to offsetthe crosswind force. This is done by steering the sea-plane in a downwind arc as shown in figure 6-5. Duringthe approach, the pilot merely plans a curved landingpath and follows this path to produce sufficient cen-trifugal force to counter the wind force. During thelanding run, the pilot can adjust the amount of centrifu-gal force by varying rudder pressure to increase or

decrease the rate of turn. This technique allows thepilot to compensate for a changing wind force duringthe water run.

Figure 6-5 shows that the tightest curve of the down-wind arc is during the time the seaplane is traveling atlow speed. Faster speeds reduce the crosswind effect,and at very slow speeds the seaplane can weathervaneinto the wind without imposing large side loads orstresses. Again, experience plays an important part insuccessful operation during crosswinds. It is essentialthat all seaplane pilots have thorough knowledge andskill in these maneuvers.

Figure 6-3. Improper technique or excessive crosswind forces can result in an accident.

VerticalComponent

HorizontalComponent

Angle Exaggeratedfor Clarity.

Figure 6-4. Dropping the upwind wing uses a horizontal com-ponent of lift to counter the drift of a crosswind.

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DOWNWIND LANDINGAlthough downwind landings often require signifi-cantly more water area, there are occasions when theyare more convenient or even safer than landing into thewind. Sometimes landing upwind would mean a long,slow taxi back along the landing path to get to the dockor mooring area. If winds are less than 5 knots and thereis ample room, landing downwind could save taxi time.Unless the winds are light, a downwind landing is sel-dom necessary. Before deciding to land downwind, thepilot needs a thorough knowledge of the landing char-acteristics of the seaplane as well as the environmentalfactors in the landing area.

As with a downwind landing in a landplane, the mainconcern for a seaplane is the additional groundspeedadded by the wind to the normal approach speed. Theairspeed, of course, is the same whether landingupwind or downwind, but the wind decreases ground-

speed in upwind landings and increases groundspeedin downwind landings. While a landplane pilot seldomthinks about the additional force placed on the landinggear by a higher groundspeed at touchdown, it is a seri-ous concern for the seaplane pilot. A small increase inwater speed translates into greatly increased water dragas the seaplane touches down, increasing the tendencyof the seaplane to nose over. In light winds, this usuallypresents little problem if the pilot is familiar with howthe seaplane handles when touching down at higherspeeds, and is anticipating the increased drag forces. Inhigher winds, the nose-down force may exceed theability of the pilot or the flight controls to compensate,and the seaplane will flip over at high speed. If thewater’s surface is rough, the higher touchdown speedalso subjects the floats and airframe to additionalpounding.

If there is a strong current, the direction of water flowis a major factor in choosing a landing direction. Thespeed of the current, a confined landing area, or the sur-face state of the water may influence the choice oflanding direction more than the direction of the wind.In calm or light winds, takeoffs usually are made in thesame direction as the flow of the current, but landingsmay be made either with or against the flow of the cur-rent, depending on a variety of factors. For example,on a narrow river with a relatively fast current, thespeed of the current is often more significant than winddirection, and the need to maintain control of the sea-plane at taxi speed after the landing run may presentmore challenges than the landing itself. It is imperativethat even an experienced seaplane pilot obtain detailedinformation about such operations before attemptingthem for the first time. Often the best source of infor-mation is local pilots with comprehensive knowledgeof the techniques that work best in specific locationsand conditions.

GLASSY WATER LANDINGFlat, calm, glassy water certainly looks inviting andmay give the pilot a false sense of safety. By its nature,glassy water indicates no wind, so there are no con-cerns about which direction to land, no crosswind toconsider, no weathervaning, and obviously no roughwater. Unfortunately, both the visual and the physicalcharacteristics of glassy water hold potential hazardsfor complacent pilots. Consequently, this surface con-dition is frequently more dangerous than it appears fora landing seaplane.

The visual aspects of glassy water make it difficult tojudge the seaplane’s height above the water. The lackof surface features can make accurate depth percep-tion very difficult, even for experienced seaplanepilots. Without adequate knowledge of the seaplane’s

CentrifugalForce

SkiddingForce

Figure 6-5. A downwind arc is one way to compensate for acrosswind.

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height above the surface, the pilot may flare too high ortoo low. Either case can lead to an upset. If the seaplaneflares too high and stalls, it will pitch down, very likelyhitting the water with the bows of the floats and flip-ping over. If the pilot flares too late or not at all, theseaplane may fly into the water at relatively high speed,landing on the float bows, driving them underwater andflipping the seaplane. [Figure 6-6]

Besides the lack of surface features, the smooth,reflecting surface can lead to confusing illusions asclouds or shore features are reproduced in stunningdetail and full color. When the water is crystal clear andglassy, the surface itself is invisible, and pilots mayinadvertently judge height by using the bottom of thelake as a reference, rather than the water surface.

The lack of surface texture also presents a physicalcharacteristic that adds slightly to the risk of glassywater landings. A nice smooth touchdown can result infaster deceleration than expected, for the same reasonthat the floats seem to stick to the surface during glassywater takeoffs: there is less turbulence and fewer airbubbles between the float bottoms and the water, whicheffectively increases the wetted surface area of thefloats and causes higher drag forces. Naturally, thissudden extra drag at touchdown tends to pull the nosedown, but if the pilot is expecting it and maintains theplaning attitude with appropriate back pressure, thetendency is easily controlled and presents no problem.

There are some simple ways to overcome the visualillusions and increase safety during glassy water land-ings. Perhaps the simplest is to land near the shoreline,using the features along the shore to gauge altitude. Becertain that the water is sufficiently deep and free ofobstructions by performing a careful inspection from asafe altitude. Another technique is to make the finalapproach over land, crossing the shoreline at the lowestpossible safe altitude so that a reliable height referenceis maintained to within a few feet of the water surface.

When adequate visual references are not available,make glassy water landings by establishing a stable

descent in the landing attitude at a rate that will pro-vide a positive, but not excessive, contact with thewater. Recognize the need for this type of landing inample time to set up the proper final approach. Alwaysperform glassy water landings with power. Perform anormal approach, but prepare as though intending toland at an altitude well above the surface. For exam-ple, in a situation where a current altimeter setting isnot available and there are few visual cues, this alti-tude might be 200 feet above the surface. Landingpreparation includes completion of the landing check-list and extension of flaps as recommended by themanufacturer. The objective is to have the seaplaneready to contact the water soon after it reaches the tar-get altitude, so at approximately 200 feet above thesurface, raise the nose to the attitude normally used fortouchdown, and adjust the power to provide a constantdescent rate of no more than 150 feet per minute(f.p.m.) at an airspeed approximately 10 knots abovestall speed. Maintain this attitude, airspeed, and rate ofdescent until the seaplane contacts the water. Once thelanding attitude and power setting are established, theairspeed and descent rate should remain the samewithout further adjustment, and the pilot shouldclosely monitor the instruments to maintain this stableglide. Power should only be changed if the airspeed orrate of descent deviate from the desired values. Do notflare, but let the seaplane fly onto the water in the land-ing attitude. [Figure 6-7]

Upon touchdown, apply gentle back pressure to theelevator control to maintain the same pitch attitude.Close the throttle only after the seaplane is firmly onthe water. Three cues provide verification throughthree different senses—vision, hearing, and body sen-sation. The pilot sees a slight nose-down pitch attouchdown and perhaps spray thrown to the sides bythe floats, hears the sound of the water against thefloats, and feels the deceleration force. Accidents haveresulted from cutting the power suddenly after the ini-tial touchdown. To the pilot’s surprise, a skip had takenplace and as the throttle closed, the seaplane was 10 to15 feet in the air and not on the water, resulting in astall and substantial damage. Be sure all of the cues

Flare Too Early Stall

Failure to Flare

Figure 6-6.The consequences of misjudging altitude over glassy water can be catastrophic.

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indicate that the seaplane is staying on the waterbefore closing the throttle. After the seaplane settlesinto a displacement taxi, complete the after-landingchecklist and lower the water rudders.

An accurately set altimeter may allow the pilot to setup for the touchdown at an altitude somewhat closerto the surface. If the pilot can be certain that the land-ing configuration and 150 f.p.m. descent will beestablished well above the water’s surface, startingthe final glide nearer the surface shortens the descenttime and overall landing length.

This technique usually produces a safe, comfortablelanding, but the long, shallow glide consumes consid-erable landing distance. Be certain there is sufficientroom for the glide, touchdown, and water run.

ROUGH WATER LANDINGRough is a very subjective and relative term. Waterconditions that cause no difficulty for small boats canbe too rough for a seaplane. Likewise, water that posesno challenge to a large seaplane or an experiencedpilot may be very dangerous for a smaller seaplane ora less experienced pilot.

Describing a typical or ideal rough water landing pro-cedure is impractical because of the many variablesthat affect the water’s surface. Wind direction andspeed must be weighed along with the surface condi-tions of the water. In most instances, though, make theapproach the same as for any other water landing. Itmay be better, however, to level off just above thewater surface and increase the power sufficiently tomaintain a rather flat attitude until conditions appearmore acceptable, and then reduce the power to touchdown. If severe bounces occur, add power and lift offto search for a smoother landing spot.

In general, make the touchdown at a somewhat flatterpitch attitude than usual. This prevents the seaplanefrom being tossed back into the air at a dangerouslylow airspeed, and helps the floats to slice through thetops of the waves rather than slamming hard againstthem. Reduce power as the seaplane settles into thewater, and apply back pressure as it comes off the stepto keep the float bows from digging into a wave face.If a particularly large wave throws the seaplane intothe air before coming off the step, be ready to applyfull power to go around.

Avoid downwind landings on rough water or in strongwinds. Rough water is usually an indication of strongwinds, and vice versa. Although the airspeed for land-ing is the same, wind velocity added to the seaplane’snormal landing speed can result in a much highergroundspeed, imposing excessive stress on the floats,increasing the nose-down tendency at touchdown, andprolonging the water run, since more kinetic energymust be dissipated. As the seaplane slows, the ten-dency to weathervane may combine with the motioncreated by the rough surface to create an unstablesituation. In strong winds, an upwind landing meansa much lower touchdown speed, a shorter water run,and subsequently much less pounding of the floatsand airframe.

Likewise, crosswind landings on rough water or instrong winds can leave the seaplane vulnerable to cap-sizing. The pitching and rolling produced by the watermotion increases the likelihood of the wind lifting awing and flipping the seaplane.

There is additional information on rough water land-ings in Chapter 8, Emergency Open Sea Operations.

CONFINED AREA LANDINGOne of the first concerns when considering a landingin a confined area is whether it is possible to get out

200 Feet

Establish Landing Attitude and150 f.p.m. Descent at 200 Feet

Maintain Landing Attitude, Airspeed, andDescent Rate All the Way to the Water

After Landing, CloseThrottle and MaintainPlaning Attitude

Perform a Normal Approach, but Set Upto Land at 200 Feet Abovethe Water Surface

Figure 6-7. Hold the landing attitude, airspeed, and 150 f.p.m. rate of descent all the way to the surface.

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again. For most seaplanes, the takeoff run is usuallymuch longer than the landing run. Before landing, thepilot should also consider the wind and surface condi-tions expected when it is time to leave. If the seaplanelands into a stiff breeze on water with small waves, itmight be more difficult to leave the next morning whenwinds are calm and the water is glassy. Conversely, ifthe seaplane lands in the morning when the air temper-ature is low, departure in the hot afternoon might meana significant loss in takeoff performance due to thedensity altitude.

It is especially important to carefully inspect thelanding area for shallow areas, obstructions, or otherhazards. After touchdown is not the time to discoverfactors that make a confined landing area evensmaller or less usable than originally supposed.Evaluation of the landing area should includeapproach and departure paths. Terrain that risesfaster than the seaplane can climb is an obvious con-sideration, both for the eventual takeoff as well as incase of a go-around during landing. If climbout overthe terrain is not easily within the seaplane’s capabilities,be certain there is sufficient room to make a gentle turnback over the water for climb.

GO-AROUNDWhenever landing conditions are not satisfactory, exe-cute a go-around. Potential conflicts with other aircraft,surface vessels or swimmers in the landing area, recog-nition of a hazard on the water, wind shear, wake tur-bulence, water surface conditions, mechanical failure,or an unstabilized landing approach are a few of thereasons to discontinue a landing attempt. Climb to asafe altitude while executing the go-around checklist,then evaluate the situation, and make another approachunder more favorable conditions. Remember that it isoften best to make a gentle climbing turn back over thewater to gain altitude, rather than climbing out over ashoreline with rising terrain or noise-sensitive areas.The go-around is a normal maneuver that must be prac-ticed and perfected like any other maneuver.

EMERGENCY LANDINGEmergency situations occurring within gliding distanceof water usually present no landing difficulty. Althoughthere is some leeway in landing attitude, it is importantto select the correct type of landing for the water condi-tions. If the landing was due to an engine failure, ananchor and paddle are useful after the landing is com-pleted.

Should the emergency occur over land, it is usuallypossible to land a floatplane with minimal damage in asmooth field. Snow covered ground is ideal if there areno obstructions. The landing should be at a slightly flat-ter attitude than normal, a bit fast, and directly into thewind. If engine power is available, landing with a small

amount of power helps maintain the flatter attitude.Just before skidding to a stop, the tail will begin to rise,but the long front portions of the floats stop the riseand keep the seaplane from flipping over.

A night water landing should generally be consideredonly in an emergency. They can be extremely danger-ous due to the difficulty of seeing objects in the water,judging surface conditions, and avoiding large wavesor swell. If it becomes necessary to land at night in aseaplane, seriously consider landing at a lighted air-port. An emergency landing can be made on a runwayin seaplanes with little or no damage to the floats orhull. Touchdown is made with the keel of the floats orhull as nearly parallel to the surface as possible. Aftertouchdown, apply full back elevator and additionalpower to lessen the rapid deceleration and nose-overtendency. Do not worry about getting stopped withadditional power applied after touchdown. It will stop!The reason for applying power is to provide additionalairflow over the elevator to help keep the tail down.

In any emergency landing on water, be as prepared aspossible well before the landing. Passengers and crewshould put on their flotation gear and adjust it prop-erly. People sitting near doors should hold the liferaftsor other emergency equipment in their laps, so no onewill need to try to locate or pick it up in the scrambleto exit the seaplane. Unlatch all the doors prior totouchdown, so they do not become jammed due todistortion of the airframe. Brief the passengers thor-oughly on what to do during and after the landing.These instructions should include how to exit theseaplane even if they cannot see, how to get to thesurface, and how to use any rescue aids.

POSTFLIGHT PROCEDURESAfter landing, lower the water rudders and completethe after-landing checklist. The flaps are usually raisedafter landing, both to provide better visibility and toreduce the effects of wind while taxiing. It is a goodpractice to remain at least 50 feet from any other ves-sel during the taxi.

After landing, secure the seaplane to allow safeunloading, as well as to keep winds and currentsfrom moving it around. Knowing a few basic termsmakes the following discussions easier to under-stand. Anchoring uses a heavy hook connected tothe seaplane by a line or cable. This anchor digsinto the bottom due to tension on the line, and keepsthe seaplane from drifting. Mooring means to tiethe seaplane to a fixed structure on the surface. Theseaplane may be moored to a floating buoy, or to apier, or to a floating raft. For this discussion, dock-ing means securing the seaplane to a permanentstructure fixed to the shore. To beach a seaplanemeans to pull it up onto a suitable shore surface, sothat its weight is supported by relatively dry ground

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rather than water. Ramping is defined as using aramp to get the seaplane out of the water and ontothe shore.

ANCHORINGAnchoring is the easiest way to secure a seaplane onthe water surface. The area selected should be out ofthe way of moving vessels, and in water deep enoughthat the seaplane will not be left aground during lowtide. The holding characteristics of the bottom areimportant in selecting an appropriate anchorage. Thelength of the anchor line should be about seven timesthe depth of the water. After dropping the anchor withthe seaplane headed into the wind, allow the seaplaneto drift backward to set the anchor. To be sure theanchor is holding, watch two fixed points somewhereto the side of the seaplane, one farther away than theother, that are aligned with each other, such as a tree onthe shore and a mountain in the distance. If they do notremain aligned, it means that the seaplane is driftingand dragging its anchor along the bottom. The nauticalterm for when two objects appear directly in line, onebehind the other, is “in range” and the two objects arecalled a range.

When choosing a place to anchor, think about what willhappen if the wind shifts. Allow enough room so thatthe seaplane can swing around the anchor without strik-ing nearby obstacles or other anchored vessels. Be cer-tain the water rudders are retracted, as they caninterfere with the seaplane’s ability to respond to windshifts.

If anchoring the seaplane overnight or for longer peri-ods of time, use a heavier anchor and be sure to complywith maritime regulations for showing an anchor lightor daytime visual signals when required. [Figure 6-8]

When leaving the seaplane anchored for any length oftime, it is a good idea to secure the controls with theelevator down and rudder neutral. Since the seaplanecan rotate so that it always faces into the wind, thisforces the nose down and reduces the angle of attack,keeping lift and wind resistance at a minimum.

MOORINGMooring a seaplane eliminates the problem of theanchor dragging. A permanent mooring installationconsists of a heavy weight on the bottom connected bya chain or cable to a floating buoy with provisions forsecuring mooring lines. Approach a mooring at a verylow speed and straight into the wind. To keep fromoverrunning the mooring, shut down the engine earlyand let the seaplane coast to the mooring. If necessary,the engine can be started again for better positioning.

Never straddle a buoy with a twin-float installation.Always approach while keeping the buoy to the out-side of the float to avoid damage to the propeller andunderside of the fuselage. Initial contact with the buoyis usually made with a boat hook or a person standingon the deck of one float.

While approaching the mooring, have the person onthe float secure one end of a short line to the bottom ofa float strut, if one is not there already. Then taxi theseaplane right or left of the mooring so that the float onwhich the person is standing comes directly alongsidethe buoy. The free end of the line can then be securedto the mooring.

Exercise extreme caution whenever a person is assist-ing in securing the seaplane. There have been manyinstances of helpers being struck by the propeller. On

Figure 6-8. Anchoring.

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most floatplanes, the floats extend well in front of thepropeller arc. Eager to do a good job, an inexperiencedhelper might forget the spinning propeller while walk-ing forward along the float.

DOCKINGThe procedure for docking is essentially the same asfor mooring, except that approaching directly into thewind may not be an option. The keys to successfuldocking are proper planning of the approach to thedock, compensating for the existing environmentalconditions, and skill in handling the seaplane in con-gested areas. Bear in mind that a seaplane is fragile andhitting an obstruction can result in extensive damage.

Plan the approach to the dock so as to keep the wind onthe seaplane’s nose as much as possible. While stillwell clear of the dock area, check the responsiveness ofthe water rudders and be sure the seaplane will be ableto maneuver in the existing wind and current. If controlseems marginal, turn away and plan an alternativemethod of reaching the dock. While approaching thedock, the person who will be jumping out to secure theseaplane should take off seatbelts and unlatch the door.When it is clear that the seaplane will just make it tothe dock, shut down the engine and let the seaplanecoast the remaining distance to encounter the dock asgently as possible. The person securing the seaplaneshould step out onto the float, pick up the mooring lineattached to the rear float strut, and step onto the dock asthe seaplane stops. The line should be secured to amooring cleat on the dock. Use additional mooringlines if the seaplane will be left unattended. Be sure tocomplete any remaining items on the checklist, and todouble-check that the mixture, magnetos, and masterswitch are in the off positions.

BEACHINGSuccess in beaching depends primarily on the type andfirmness of the shoreline. Inspect the beach carefullybefore using it. If this is impossible, approach the beachat an oblique angle so the seaplane can be turned outinto deeper water if the beach is unsatisfactory. Thehardest packed sand is usually near the water’s edgeand becomes softer where it is dry, further from thewater’s edge. Rocky shorelines are likely to damagethe floats, especially if significant waves are rolling in.Mud bottoms are usually not desirable for beaching.

To protect them from damage, water rudders should beup before entering the shallow water near a beach. Sandis abrasive and erodes any protective coatings on thebottoms of the floats. If possible, beach the seaplane bysailing backward with the water rudders up. The aftbottoms of the floats do not dig into the sand as deeplyas the forward bottoms, so backing onto a beach is notas hard on the floats as going in nose-first.

Do not leave the seaplane unattended unless at least atail line is fastened to some solid object ashore.Moderate action of the water rapidly washes away thesand under the floats and lets the seaplane drift. Anincoming tide can float a beached seaplane in just a fewminutes. Likewise, a receding tide may leave a sea-plane stranded 30 or 40 feet from the water in a fewhours. Even small waves may alternately pick up anddrop the seaplane, potentially causing serious damage,unless the seaplane is beached well out of their reach.Flying boat pilots should be sure to clear the main gearwells of any sand or debris that may have accumulatedbefore departing.

If the seaplane is beached overnight or higher windsare expected, use portable tiedowns or stakes driveninto firm ground and tie it down like a landplane. Ifsevere winds are expected, the compartments of thefloats can be filled with water. This holds the seaplanein very high winds, but it is a lot of work to pump outthe floats afterward.

RAMPINGFor the purpose of this discussion, a ramp is a slopingplatform extending well under the surface of the water.If the ramp is wood, the seaplane can be slid up ordown it on the keels of the floats, provided the surfaceof the ramp above the water is wet. Concrete boatramps are generally not suitable for seaplanes. Waterrudders should be down for directional control whileapproaching the ramp, but raised after the seaplane hitsthe ramp.

If the wind is blowing directly toward the shore, it ispossible to approach the ramp downwind with enoughspeed to maintain control. Continue this speed until theseaplane actually contacts the ramp and slides up it.Many inexperienced pilots make the mistake of cuttingthe power before reaching the ramp for fear of hitting ittoo hard. This is more likely to result in problems, sincethe seaplane may weathervane and hit the ramp side-ways or backward, or at least need to be taxied out foranother try. When approaching at the right speed, thebow wave of the float cushions the impact with theramp, but if the seaplane is too slow or decelerating,the bow wave moves farther back along the float andthe impact with the ramp may be harder. Many pilotsapply a little power just prior to hitting the ramp, whichraises the fronts of the floats and creates more of acushioning bow wave. Be sure to hold the elevator con-trol all the way back throughout the ramping.[Figure 6-9]

When the seaplane stops moving, shut down the engineand complete the appropriate checklist. Ideally, the sea-plane should be far enough up the ramp that waves orswells will not lift the floats and work the seaplane

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back into the water, but not so far up the ramp thatshoving off is difficult. Ramps are usually quite slip-pery, so pilot and passengers must be very cautious oftheir footing when walking on the ramp.

The most difficult approach is when the wind is blow-ing parallel to the shore, and strong enough to makecontrol marginal. If the approach is made into the wind,it may not be possible to turn the seaplane crosswindtoward the ramp without excessive speed. In mostcases, the best procedure is to taxi directly downwinduntil near the ramp, then close the throttle at the rightpoint to allow weathervaning to place the seaplane onthe ramp in the proper position. Then apply power topull the seaplane up the ramp and clear of the water.This should not be attempted if the winds are high or

the ramp is too slippery, since the seaplane could beblown sideways off the leeward side of the ramp.[Figure 6-10]

Experience and proficiency are necessary for rampingin strong winds. In many instances, the safest proce-dure is to taxi upwind to the ramp and near enough fora helper to attach a line to the floats. The seaplane maythen be left floating, or pushed and pulled into a posi-tion where a vehicle can haul it up the ramp.

SALT WATERAny time the seaplane has been operated in salt water,be sure to flush the entire seaplane with plenty of freshwater to minimize corrosion.

Approach Rampfrom Upwind Side

Allow Wind toWeathervane the Seaplane UntilLined Up with theRamp. Use Powerto Pull the Seaplane Wellonto the Ramp.

Figure 6-9.The bow wave cushions the contact with the ramp.

Figure 6-10. Crosswind approach to a ramp.

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